Document and test flags in x509_verify
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index cd6e292..b11ab84 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -482,6 +482,7 @@
                                               NULL, NULL );
 
     TEST_ASSERT( ret == exp_ret );
+    TEST_ASSERT( flags == (uint32_t)( -1 ) );
 exit:
     mbedtls_x509_crt_free( &crt );
     mbedtls_x509_crt_free( &ca );